System for Drying a Paste-Based Crafting Medium During Three-Dimensional Printing

ABSTRACT

This invention relates to three-dimensional printing. This invention in particularly relates to a system for drying a paste-based crafting medium during three-dimensional printing and a method thereof. The system can comprise a dual printhead comprising a first dispensing nozzle for depositing the filament material for a mold layer in a flowable fluid form and a second dispensing nozzle for depositing the crafting medium, which is in a paste form. The system also includes a drying means which can be a heating system or a drying apparatus, that in some embodiments can be attached to the printhead. The three-dimensional imaging process for making objects, preferably metal objects or ceramic objects, on a layer-by-layer basis under the control of a data processing system is disclosed. The drying of the object or mold is crucial in the three-dimensional imaging process because it can affect the overall quality of the object. A solution to this problem is achieved in the present invention by using a drying step after finishing each layer of the object (both mold and paste). This is achieved in some embodiments by using a drying apparatus comprising a radiating heater and air circulation fan mounted on to the moving print head. The print head can repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled manner. This system and method provides improved evenness in the drying and reduces the risk of cracks developing in the deposited object, and also reduces the risk of further problems during the subsequent processing steps to provide the finished object.

FIELD OF THE INVENTION

The present invention generally relates to the field of three-dimensional (“three-dimensional) printing of objects based on crafting and molding techniques. The invention particularly relates to a system for drying a paste-based crafting medium during three-dimensional printing and a method thereof.

BACKGROUND OF THE INVENTION

Three-dimensional printers are used to build solid models by performing layer by layer printing of a building material. The building material can be of different forms, such as a liquid or a semiliquid at the three-dimensional printhead. For example, a solid material can be heated and then extruded from a three-dimensional printer nozzle. The layers of building materials can be solidified on a substrate. Three-dimensional printer systems can use a fused filament fabrication (FFF) process (sometimes called fused deposition modeling (FDM) process) in which a filament is moved by a filament moving mechanism, toward a heated zone. The filament can be melted and extruded on a platform to form a three-dimensional object. The melted filament can adhere to the walls of the heated printhead, resulting in deformed printed lines. A commercially available

FFF system uses a heated nozzle to extrude a melted material such as a plastic wire. The starting material is in the form of a filament which is being supplied from a spool. The filament is introduced into a flow passage of the nozzle and is driven to move like a piston inside this flow passage. The front end, near the nozzle tip, of this piston is heated to become melted. The rear end or solid portion of this piston pushes the melted portion forward to exit through the nozzle tip. The nozzle is translated under the control of a computer system in accordance with previously generated computer-aided design (“CAD”) data that has been sliced into constituent layers.

A number of different types of accessories for three-dimensional printing are described in the prior art. For example, the following patents are provided for their supportive teachings and are all incorporated by reference: Prior art document, U.S. Pat. No. 5,121,329 to S Scott Crump discloses an apparatus for making three-dimensional physical objects of a predetermined shape by sequentially depositing multiple layers of solidifying material on a base member in a desired pattern. The reference does not appear to disclose the formation of a mold (“mould”) or use of any crafting medium.

Another prior art document, US20140291886 to Mark et al discloses three-dimensional printers, and reinforced filaments, and their methods of use. In one embodiment, a void free reinforced filament is fed into an extrusion nozzle. The reinforced filament includes a core, which may be continuous or semi-continuous, and a matrix material surrounding the core. The reinforced filament is heated to a temperature greater than a melting temperature of the matrix material and less than a melting temperature of the core prior to extruding the filament from the extrusion nozzle. The three-dimensional printer further includes the heating element which is used to heat the core and/or surrounding material.

Yet another prior art document, U.S. Pat. No. 8,827,684 to Schumacher et al discloses a fused filament fabrication printer which has a fixed extrusion module having multiple print heads having print tips. The fixed arrangement of the printing heads allows the close spacing of multiple print tips in a print head unit, and the simple routing of multiple plastic or metal filaments to the individual printing heads. The closely spaced print tips in the print head unit share common components. An exemplary print head unit has four printing heads which share a common heating block and heating block temperature sensor. However, this prior art document does not appear to discuss metal or ceramic object formation or the use of paste crafting medium.

Yet another prior art document, US20150174824 to Gifford discloses a modular three-dimensional printer system including a base subsystem and multiple exchangeable components. The base subsystem can have a three-dimensional motion module, a printhead module and a platform module. The multiple exchangeable components can include printheads having different configurations and functionalities, which can be exchangeably installed in the printhead module. In one of the embodiments, the system has radiant heat source, which is located on the moving printhead in such a way as to focus the heat in the area that is about to be fused. The heated substrate can increase the penetration of the bond between the substrate and the freshly deposited material. This document fails to discuss the drying of finished layers by heating or by air.

Yet another prior art documents, U.S. Pat. No. 9,833,839 and U.S. Pat. No. 9,815,118 both discloses similar techniques for fabricating support structures, breakaway layers, and the like suitable for use with sinterable build materials. The furnace or heating device is used at the post-processing steps and/or for sintering into a densified object. Further, the system may also include temperature control system at the build plate for fabricating the object. However, these prior art documents do not appear to discuss the drying of the second material or second binder (which is the crafting medium) by heating or by air.

Yet another prior art document, U.S. Pat. No. 8,475,946 to Dion et al discloses a method of preparing a ceramic precursor article, the ceramic precursor made thereby, a method of making a ceramic article and an article made by that method. It also includes a method of replicating a ceramic shape. This prior art document describes that one of the main challenges of the use of ceramic products with modern technologies is its reduction factor (shrinkage). Depending on the processes used, drying, firing or hot pressing of a ceramic object can cause shrinkage as high as 20 percent. Such shrinkage can cause a significant problem if the nature of the ceramic article requires precise dimensional control. Yet another prior art document, US20110129640 to Beall et al discloses a method for making porous articles, including: depositing a powder mixture layer comprising a binder powder, and at least one structural powder; contacting the powder mixture layer and an aqueous liquid to selectively activate the binder powder and form a green layer; repeating the depositing and the contacting sequence at least one time; and de-powdering and drying of the resulting green body. In this prior art document, the drying is carried out at the end of the processing. This document fails to discuss the drying of finished layers by heating or by air.

Yet another prior art document, SE1500245 to Mats Moosberg discusses a three-dimensional imaging process for making objects, preferably metal objects or ceramic objects, on a layer-by-layer basis under the control of a data processing system. The process also includes the use of a filament material (in the form of a solid that melts to a fluid during the printing process) to build the mold and a crafting medium (in the form of paste) for filling the hollow mold cavity. The method for building the three-dimensional model by extruding a crafting medium in parallel with a molding material as described in the prior art document, SE1500245, requires that the crafting medium paste is dried after the creation of the object. The drying process is evacuating all water from the paste and leave a dry “green body”, similar to dried clay. The problem which needs to be addressed here is that the paste needs to be dried evenly to avoid cracks. It is also important that the paste is dried fully in the middle to avoid problems in the next steps.

Yet another prior art document, WO2018/200512, to Thomas Gregory Mark, discusses printing with a print head part layers containing a binder, followed by debinding of all or part of the binder or the layer before depositing a plurality of subsequent layers. Various means for achieving this are disclosed, such as utilizing a debinding head that continuously track the print head. The methods and compositions of the present invention are distinguished from the reference which requires that at least some of the layers are partially or fully debound, because the present invention instead teaches drying of the layer, which corresponds to removal of some or substantially all of the solvent or carrier component, which in some embodiments of the present invention is an aqueous solvent. The distinction is that the prior reference teaches the removal of the binder itself, while the present invention is instead directed to drying the layer to remove the solvent or carrier while leaving behind the binder. Leaving the binder is useful to help maintain the structural integrity of the printed object prior to further processing.

However, above mentioned references and many other similar references has one or more of the following shortcomings: (a) not discussing molding technique; (b) not discussing the use of building or crafting medium; (c) prior art three-dimensional-printing methods use a powder clay which is mixed with water and printed out on a layer by layer basis using a syringe to obtain ceramic objects; (d) ceramic object may have low resolution; (e) finishing of the final three-dimensional printed object is not good; and (f) none of the references discusses drying of the paste or crafting medium or building material layer by layer to ensure uniform drying. A solution to this problem is achieved in the present patent application by adding a drying step after finishing each layer of the object (both mold and paste). This is achieved by using drying apparatus consisting of radiating heater and air circulation fan mounted on to the moving print head , the print head can repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled way.

The present application addresses the above-mentioned concerns and short comings with regard to providing an improved system for drying a paste based crafting medium during three-dimensional printing and a method thereof.

SUMARY OF THE INVENTION

This invention relates to three-dimensional printing utilizing a system and method for drying, i.e. removing the solvent or carrier from the binder component, of a paste-based crafting medium used for the printing. The system can comprise a dual printhead having a first dispensing nozzle for depositing the filament material for a mold in a flowable fluid form and a second dispensing nozzle for depositing the crafting medium, which is in a paste form. The drying of the object or mold is very crucial in the three-dimensional imaging process because it also affects the overall quality of the object. A solution to this problem is achieved in the present invention by adding a drying step after finishing each layer of the object (both mold and paste). This is achieved by using drying apparatus consisting of radiating heater and air circulation fan mounted on a moving head, the head can repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled way. This will enable better evenness in the drying and reduce risks for cracks and also reduces problems in the next steps.

The present invention relates to a method for three-dimensionally printing, i.e. a method for three-dimensional printing using, a paste-based crafting medium (i.e. material) comprising the steps of:

(a) depositing a layer of a crafting medium with a print head, and

(b) drying the deposited layer from step (a) with a drying means.

In further embodiments the present invention relates to a method wherein steps (a) and (b) are performed prior to deposition of a further crafting medium layer.

In further embodiments the present invention relates to a method wherein the drying step (b) comprises point drying of the deposited layer.

In further embodiments the present invention relates to a method wherein the drying step (b) comprises full area drying of the deposited layer.

In further embodiments the present invention relates to a method wherein the drying means is provided by a drying head.

In further embodiments the present invention relates to a method wherein the drying means is selected from a radiating heater, an infra-red heater, a circulating convective heater, a hot gas blowing heater, a contact heater, a resistance heater, or a microwave heater.

In further embodiments the present invention relates to a method wherein the drying head follows the same trajectory as the print head.

In further embodiments the present invention relates to a method wherein the drying head is attached to and trails the print head.

In further embodiments the present invention relates to a method wherein the drying head follows a trajectory that is different from that of the print head.

In further embodiments the present invention relates to a method wherein the deposited layer of the crafting medium is heated to a temperature from about 20° C. to about 100° C. for deposition.

In further embodiments the entire chamber or print volume is elevated in temperature and/or dehumidified while the crafting medium is being deposited or after the printing has been completed.

In further embodiments the present invention relates to a method comprising drying the deposited layer from step (a) while simultaneously or subsequently decreasing the atmospheric pressure surrounding the crafting medium to facilitate said drying.

In further embodiments the present invention relates to a method wherein the crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of an aqueous         solvent.

In further embodiments the crafting medium comprises one or more binders or binder components.

In further embodiments the present invention relates to a method wherein the crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of a non-aqueous         solvent.

In further embodiments the present invention relates to a method wherein the crafting medium comprises:

-   -   (i) from about 60% to about 70% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 1% to about 5% by volume of a binder; and     -   (iii) from about 25% to about 35% by volume of an aqueous         solvent.

In further embodiments the present invention relates to a method wherein the crafting medium comprises:

-   -   (i) from about 60% to about 70% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 1% to about 5% by volume of a binder; and     -   (iii) from about 25% to about 35% by volume of a non-aqueous         solvent.

In further embodiments the present invention relates to a method wherein the drying step (b) removes substantially all of the aqueous or non-aqueous solvent from the deposited layer (a).

In further embodiments the present invention relates to a method wherein the drying step (b) removes at least about 90% by weight of the aqueous or non-aqueous solvent from the deposited layer (a).

In further embodiments the present invention relates to a method wherein the drying step (b) removes at least about 95% by weight of the aqueous or non-aqueous solvent from the deposited layer (a).

In further embodiments the present invention relates to a method wherein the drying step (b) removes at least about 99% by weight of the aqueous or non-aqueous solvent from the deposited layer (a).

In further embodiments the present invention relates to a method wherein the metal or ceramic powder comprises particles having a size in the range from 0.1-100 micrometers.

In further embodiments the present invention relates to a method wherein the metal powder is selected from silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel, metal alloys, and combinations thereof.

In further embodiments the present invention relates to a method wherein the ceramic powder is selected from silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate, zirconia, and combinations thereof.

In further embodiments the present invention relates to a method wherein the binder is selected from organic binders, inorganic binders, and combinations thereof.

In further embodiments the present invention relates to a method wherein the inorganic binder is selected from epoxy, polyurethane, agar-agar, starch, cellulosic materials, arrow root, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dammar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide, polycarboxylic acids (polyacrylic acid), polycarboxylate ethers, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, and combinations thereof.

In further embodiments the present invention relates to a method wherein the inorganic binder is selected magnesium oxide, magnesic, cement, sorel cement, inorganic salts, and combinations thereof.

In further embodiments the present invention relates to a method wherein said aqueous solvent is selected from water, or water in combination with one or more non-aqueous solvents selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, C4-alcohols, 2-ethoxyethanol, 2-ethyl hexanol, 1,2-dichloroethane, diisopropyl amine, isoamyl alcohol, propyl acetate, isopropyl acetate, and mixtures thereof. Also, contemplated are azeotropes.

In further embodiments the present invention relates to a method wherein said non-aqueous solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, and mixtures thereof.

In further embodiments the present invention relates to a method for drying a paste-based crafting medium during three-dimensional printing of an object comprising the steps of:

(a) depositing a layer of a crafting medium with a print head, and

(b) drying the deposited layer from step (a) with a drying means.

In further embodiments the present invention relates to a drying method wherein said crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of an aqueous         solvent.

In further embodiments the present invention relates to a drying method wherein said crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of a non-aqueous         solvent.

In further embodiments the present invention relates to a method for three-imensionally printing a paste-based crafting medium comprising the steps of:

-   -   (a) depositing a mold layer from a print head,     -   (b) depositing a layer of a crafting medium with a print head         within the confines of the mold layer, said crafting medium         comprising:     -   (c) drying the deposited layer from step (b) with a drying         means.

In further embodiments the present invention relates to a method wherein steps (a), (b), and (c) are performed prior to deposition of a further crafting medium layer.

In further embodiments the present invention relates to a method wherein the crafting medium deposited in step (b) is deposited at a volume in excess of the volume defined by the mold layer.

In further embodiments the present invention relates to a method wherein the excess crafting medium deposited in step (b) is removed prior to drying in step (c).

In further embodiments the present invention relates to a method wherein the removal is performed by scraping or suction, or a combination of thereof.

In further embodiments the present invention relates to a method wherein the excess crafting medium deposited in step (b) is removed subsequent to drying in step (c).

In further embodiments the present invention relates to a method wherein the removal is performed by milling, scraping, or suction, or a combination theerof.

In further embodiments the present invention relates to a method wherein the mold layer comprises a thermoplastic polymer.

In further embodiments the present invention relates to a method wherein the thermoplastic polymers is selected from the group consisting of poly(propylene), poly(styrene), poly(lactic acid) (PLA), acrylonitrilebutadiene-styrene (ABS), polycarbonate abs (PC-ABS), nylon, poly(carbonate), poly(phenyl sulfone), ultem, poly(ethylene), acrylic [poly(methyl methacrylate)], poly(benzimidazole), poly(ether sulfone), poly(etherether ketone), poly(etherimide), poly(phenylene oxide), poly(phenylene sulfide), poly(vinyl chloride), poly(vinyldiene fluoride), poly(acetal), poly(vinyl acetate), poly(vinyl butyrate), poly(vinyl alcohol), poly(4-hydroxystyrene), poly(vinyl formate), poly(vinyl stearate), poly(acrylamide), poly(caprolactone), chitosan and combinations thereof.

In further embodiments the present invention relates to a method wherein said crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of an aqueous         solvent.

In further embodiments the present invention relates to a method wherein said crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of a non-aqueous         solvent.

In further embodiments the present invention relates to a three-dimensionally printed article of manufacture prepared according to the methods described herein.

In further embodiments the present invention relates to a three-dimensionally printed article prior to sintering.

In further embodiments the present invention relates to a system for continuously drying a paste-based crafting medium during three-dimensional printing comprising:

(a) a print head for depositing a layer of a crafting medium, and

(b) a drying means for subsequently drying each deposited layer (a).

In further embodiments the present invention relates to a system for continuously drying a paste-based crafting medium during three-dimensional printing comprising:

-   -   (a) a print head for depositing a mold layer;     -   (b) a print head for depositing a layer of a crafting medium         within the confines of the mold layer; and     -   (c) a drying means for subsequently drying each deposited layer         (b).

In further embodiments the present invention relates to a system wherein said crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of an aqueous         solvent.

In further embodiments the present invention relates to a system wherein said crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of a non-aqueous         solvent.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent when consideration is achieved to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 depicts a schematic representation of the system in accordance with the present invention.

FIG. 2 illustrates by a flow chart an example of a method for drying a paste based crafting medium during three-dimensional printing.

FIG. 3 illustrates a schematic representation of a system for carrier removal with a separate head with a suction or aspiration mechanism.

FIG. 4 illustrates an example of a toolpath for the carrier removal function.

FIG. 5 illustrates a schematic example of a full width moving head.

FIG. 6 illustrates movement of a scan of the full width moving head.

FIG. 7 illustrates as a schematic example another way to remove the carrier from the crafting medium by heating the crafting medium just before the extrusion orifice, and to include a suction or aspiration mechanism to transport the carrier away from the printing area.

FIG. 8 illustrates how when depositing a crafting medium in a layer by layer and line by line manner there is a risk for voids between the layer and lines.

FIG. 9 illustrates an embodiment with a deposition nozzle for extruding the crafting medium, where the nozzle includes a geometry for scraping off the excess material just after the extrusion point.

FIG. 10 illustrates a perspective view of a deposition nozzle with a circular knife wedge as a concentric ring surrounding the nozzle orifice.

FIG. 11 illustrates a system for removing excess crafting material before drying from the print area with a subtractive tool, such as a scraper, and suction mechanism.

FIG. 12 illustrates a system for removing the excess crafting medium after it has dried or been partially dried, i.e. when some or substantially all of the carrier for the binder has been removed from the layer, by a milling means and a suction mechanism for transporting the excess material away from the print area.

FIG. 13 illustrates an example of a toolpath for removal of excess crafting medium by milling or scraping when dried or partially dried.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural and logical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.

In further embodiments the present invention relates to a three-dimensionally printed article of manufacture prepared using the system of the present invention.

Many Rapid Prototype processes have been developed in recent years and many more are currently being researched, but until recently, few of them have been used to fabricate paste or clay-based objects. A major problem is cracking of the object when drying is carried out at the end of the processing. Cracks and unevenness can develop throughout the object. The present invention is providing a solution to solve this problem of cracks and unevenness of the object and mold. The present invention provides a system for drying a paste based crafting medium during the three-dimensional printing of the object and also a method thereof. In some embodiments, a drying means or apparatus such as a heating system is connected to a moving head. This makes drying possible after printing each layer of the object, that is, both the mold and the paste. The head can repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled manner.

As distinguished from other methods, the three-dimensional printing methods of the present invention involve partially or completely drying a portion or all of a desired deposited layer of a crafting medium. This drying corresponds to removal of some or substantially all of the solvent or carrier component associated with the binder, which in some embodiments of the present invention is an aqueous solvent.

The aqueous solvent can comprise water or water in combination with other solvents. These other solvents are generally volatile solvents that are miscible with water at the concentrations or proportions utilized for the solvent system. The volatile solvents would generally have a boiling point at atmospheric pressure of about 100° C. or less. In other embodiments, the solvent or carrier can be a nonaqueous material. The non-aqueous solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, and mixtures thereof. The present invention generally leaves behind the binder in the deposited layer, which can be advantageous to maintain the structural integrity of the printed object for further processing.

It should be appreciated that the drying described herein is essentially occurring concurrently with the layer-by-layer deposition of the deposited materials and not after the completion of the printing of the entire object. This means that the drying is performed as the crafting material is deposited, such as by a means that travels concurrently with the printing head or trails behind it. Alternatively, the drying is performed immediately after the entire layer has been deposited or some time interval thereafter. However, it is intended that the drying step on the deposited layer is performed prior to the deposition of a subsequent layer. The drying systems and methods described herein can alternatively be described as continuous drying, because the drying is performed on a layer-by-layer basis while the three-dimensional object is being printed.

It should also be appreciated that in the present invention the individually printed layers are intended to be bonded to each other as part of a solid composition after processing and sintering. The layer-by-layer drying is not intended to interfere with, but instead to facilitate the manufacture of a solid object.

FIG. 1 depicts a schematic representation of a system for drying a paste based crafting medium during three-dimensional printing according to one of the embodiments of the present invention. The system 100 for drying a paste based crafting medium during three-dimensional printing comprises: (a) supply arrangement for a filament material 101 for forming a mold layer for the object; (b) an extruder 103; (c) a feeding channel 106; (d) a plurality of nozzles 107 and 113; (e) a plurality of heating elements/systems 108 for melting the filament and 119 for drying the crafting medium; (f) a plurality of discharge orifices 109 and 114; (g) a supply arrangement for a crafting medium 110; (h) an actuator 112 for controlling the flow of the crafting medium; (i) a mold 116 (formed from the layer-by-layer deposition of the filament material); and (j) a platform 115 on which the system of three-dimensional printer is fixed. The system has dual printhead which comprise a first dispensing nozzle 107 for depositing the filament 102 in flowable fluid form by the discharge orifice 109 to supply a filament 102 or a first material layer and a second dispensing nozzle 113 for depositing a crafting medium 111 or the second material layer which is in a paste form by the discharge orifice 114. The system further comprises a holding element 118 which holds a dual printhead and a heating element/system 119.

A filament feeding device comprising a stepper motor (not shown) and idler and driving rollers 104 and 105 located opposite to drive rollers which work together to grip the filament there between and to advance it through a filament feeding channel 106 thereby regulating the flow of filament through the feeding channel. The extruder 103 can be of any different type such as roller, gear system, etc. The heating system 121 can consist of a radiating heater, and possibly an air circulation fan. The heating system may also have connectors 120, which can be of electric wire or pipes/tubes for blowing air. The heating system can also provide cooling or can reduce the temperature and can function as a temperature control system. Further, the temperature control system can include without limitation one or more of a heater, coolant, a fan, a blower, or the like.

As shown in the FIG. 1, a system 100 in accordance with a preferred embodiment of the present invention comprises a supply 101 of filament material such as acrylonitrilebutadiene-styrene (ABS) or Polylactic acid (PLA); a filament feeding device comprising a stepper motor (not shown), idler rollers 104 located opposite to driver rollers 105 which work together to grip the filament there between and to advance it through a filament feeding channel 106 thereby regulating the flow of filament through the feeding channel 106. The feeding channel 106 is made of a material having low thermal conductivity, such as for example stainless steel. The system further includes a first dispensing hot end or liquifier 107, preferably made of a material with a thermal conductivity greater than 25 W/(m·K), such as for example brass or similar metallic alloys. The first dispensing hot end or liquifier 107 can be heated to a temperature sufficiently high for the filament 102 to liquify. Heating elements 108, in the form of a resistance heating tape or sleeve, and a temperature sensor (not shown) are arranged around a lower portion of the hot end or liquifier 107 to regulate the temperature of the hot end or liquifier 107 to a temperature of approximatively 200° C. to 240° C. to convert a leading portion of the filament 102 into a flowable fluid state. The solid (un-melted) portion of the filament 102 inside the feeding channel 106 acts like a piston to drive the melted liquid for dispensing through a first discharge orifice 109. The drive motor (not shown) can be controlled to regulate the advancing rate of the filament 102 in the feeding channel 106 so that the volumetric dispensing rate of the fluid can be closely controlled.

The filament material is preferably a thermoplastic polymer that softens and liquifies for easy deposition and which rapidly cools and hardens to provide a suitable mold. Thermoplastic polymers useful for forming the mold from the filament material can include the following: poly(propylene), poly(styrene), poly(lactic acid) (PLA), acrylonitrilebutadiene-styrene (ABS), polycarbonate abs (PC-ABS), nylon, poly(carbonate), poly(phenyl sulfone), ultem, poly(ethylene), acrylic [poly(methyl methacrylate)], poly(benzimidazole), poly(ether sulfone), poly(etherether ketone), poly(etherimide), poly(phenylene oxide), poly(phenylene sulfide), poly(vinyl chloride), poly(vinyldiene fluoride), poly(acetal), poly(vinyl acetate), poly(vinyl butyrate), poly(vinyl alcohol), poly(4-hydroxystyrene), poly(vinyl formate), poly(vinyl stearate), poly(acrylamide), poly(caprolactone), chitosan and combinations thereof.

As shown in the FIG. 1, the apparatus further includes a supply of a crafting medium 111, such as for example a metal clay or a ceramic clay. In a preferred embodiment of the invention, the crafting medium 111 comprises microscopic metal particles of metal, such as silver, gold, copper, iron, or alloys or combinations thereof, mixed with an organic binder and water. The supply 110 is preferably shaped as a conventional clay extruder comprising a cylindrical cavity and valve/actuator means 112 to control and regulate the flow of crafting medium toward a second dispensing nozzle 113 and through a second discharge orifice 114.

Both nozzles 107 and 113 are arranged at a predetermined distance from an object supporting platform 115. The dual printhead and the platform 115 are moved relative to one another in a movement pattern corresponding to a predetermined object 116 and 117. The mold filament 102 is deposited through the first discharge orifice 109 while the dual printhead is moving in an X-Y-plane relative to the platform 115, to build one layer of a mold 116. Thereafter, the crafting medium 111 is deposited while the dual printhead is moving in an X-Y-plane relative to the platform 115 in order to fill the layer of the mold 116 forming 117.

The crafting medium 111 is in the paste form. The layer of the crafting medium is required to be dried immediately, or a short time interval after printing, but in any event prior to the printing of the next crafting medium layer. The system 100 includes the heating system or drying apparatus 119 which can be connected on the printhead. The heating system is used for drying a paste of the crafting medium 111. This drying is accomplished by moving the print head relative to the deposited crafting medium and it is possible after finishing each layer of the object (both mold and paste), to have the print head repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled way. The drying apparatus can comprise a radiating heater, and possibly an air circulation fan. This can enable better evenness in the drying and reduce risks for cracks and also reduce problems in subsequent processing steps.

Thereafter the dual printhead and the platform 115 are displaced in the Z-direction from one another by a distance corresponding to the thickness of a single layer so that the next layer can be deposited. The first and second dispensing nozzles 107 and 113 are used to deposit the melted filament and the crafting medium respectively and to alternate the deposition on a layer by layer basis, in such a manner that the mold is alternately built and then filled with crafting medium for each layer. When the deposition is achieved, the object 117 is embedded inside the mold 116. The mold 116 will thereafter be removed in order to release the object 117. That removal step is preferably achieved by heating the mold 116 to a temperature of approximately 200° C. until the mold building material is melted away from the object 117. If the object 117 is made of metal clay, the metal contained in the object 117 is thereafter sintered to obtain a pure metal object.

An alternate, and important, method for removing the mold material is to thermally decompose the polymer. The range of temperatures in the case of decomposition will vary depending upon the specific polymer used and the environment in which the decomposition occurs. For example, a range from about 150° C. to about 500° C. (wax is at the lower end, poly(propylene) at the higher end, for example).

In an alternate embodiment of the present invention, the apparatus further includes a heating means (not shown) for heating and melting the mold 116. Such heating means can consist of an insulated chamber, or an oven, inside which the mold 116 is exposed to heat energy to release the object 117.

A first supply of filament material used to build the mold. The supply of filament can comprise a rotatable spool on which the filament is wound. Such a filament material can be comprised of, but is not limited to, one or more of the following materials including various waxes, thermoplastic polymers, thermoset polymers, and combinations thereof. However, the primary modeling material preferably comprises an organic polymer with a reasonably low softening or melting point, e.g., acrylonitrile-butadiene-styrene (ABS) or Polylactic acid (PLA).

As described above, thermoplastic polymers useful for forming the mold from the filament material can include the following: poly(propylene), poly(styrene), poly(lactic acid) (PLA), acrylonitrilebutadiene-styrene (ABS), polycarbonate abs (PC-ABS), nylon, poly(carbonate), poly(phenyl sulfone), ultem, poly(ethylene), acrylic [poly(methyl methacrylate)], poly(benzimidazole), poly(ether sulfone), poly(etherether ketone), poly(etherimide), poly(phenylene oxide), poly(phenylene sulfide), poly(vinyl chloride), poly(vinyldiene fluoride), poly(acetal), poly(vinyl acetate), poly(vinyl butyrate), poly(vinyl alcohol), poly(4-hydroxystyrene), poly(vinyl formate), poly(vinyl stearate), poly(acrylamide), poly(caprolactone), chitosan and combinations thereof. The structural additive is selected from the group consisting of metals, charcoal particles, ceramics, or other particles.

A second supply of crafting medium can be in paste form. Such a medium can comprise silicone, a ceramic material or the like. The crafting medium is preferably a commercially available metal clay usually comprising very small particles of metal such as silver, gold, bronze, or copper mixed with an organic binder and water commonly used in making jewelry, beads and small sculptures.

FIG. 2 illustrates a flow chart as an example of a method for drying a paste based crafting medium on a layer-by-layer basis during three-dimensional printing. The process starts at the “Start” block 201. At block 202, is the extrusion and deposition of a mold material (a filament material) in a layer form. In block 202, there are several sub-steps involved (which are not depicted in the FIG. 2): such as providing a supply of mold building material in filament form; feeding the filament to enter one end of a flow passage of the first dispensing nozzle having a first discharge orifice on another end; heating the first dispensing nozzle to convert a leading portion of the filament therein to a flowable fluid; and dispensing the flowable fluid through the first discharge orifice to an object-supporting platform. Other embodiments for performing block 202 can be used.

At block 203, the crafting material is extruded and deposited in a layer form within the confines of the mold layer deposited at block 202. In block 203, there are several sub-steps involved: such as providing a supply of crafting medium in paste form; feeding the crafting medium to enter one end of a flow passage of the second dispensing nozzle having a second discharge orifice on another end; and during the dispensing step, operating the second dispensing nozzle for extruding the crafting medium on a layer.

At block 204, the drying apparatus or heating system 121 is turned on. In this embodiment, the heating system or drying apparatus is connected on the printhead. Then in the next step, block 205, the heating system or drying apparatus connected to the printhead is circulated on the crafting material layer. By circulating the printhead, the heating system is drying the paste of the crafting medium. By performing this drying after finishing each layer of the object (both mold and paste), the print head can repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled way. This layer-by-layer drying of the crafting paste will enable better evenness in the drying and reduce risks for cracks and also reduce problems in the subsequent steps of the process. Then “Turn off” the heating system or drying apparatus 121 is turned off, i.e. “Turn off” as indicated at block 206. Next at block 207, thereafter the dual printhead and the platform are displaced in Z-direction from one another by a distance corresponding to the thickness of a single layer so that the next layer can be deposited. Next at block 208, if the printing of the all layers, meaning that the crafted object and mold are complete then the object is moved to the next step, indicated as the end of the process, block 208. Otherwise, the process repeats and starts again from block 201 until the printing of the object and mold are complete.

The present invention relates to a three-dimensional imaging process for making objects, preferably metal objects or ceramic objects, on a layer-by-layer basis under the control of a data processing system. Some of the process steps which are not included above in detail are: (a) providing a dual printhead including a first dispensing nozzle and a second dispensing nozzle; (b) during the dispensing step, moving the dual printhead and the object-supporting platform relative to one another in a plane defined by first and second directions and in a third direction orthogonal to said plane to form the flowable fluid into a three-dimensional hollow pattern having a molding cavity shaped in accordance with a predetermined three-dimensional object; (c) on a layer basis through the second discharge orifice onto the three-dimensional hollow pattern in order to gradually fill the molding cavity, thereby forming the predetermined three-dimensional object; and (d) removing the three-dimensional hollow pattern in order to release the predetermined three-dimensional object.

FIG. 3 illustrates a means for drying the deposited crafting medium layer. To allow for accurate removal of the carrier a separate process can be used. This process can comprise a separate moving head 121 which removes the carrier along a toolpath. In addition, a means 301 for transporting the carrier away from the print area can be employed which can include a suction or aspiration mechanism 302.

FIG. 4 illustrates an example of a toolpath 401 for the carrier removal function as described in FIG. 3. The toolpath can be generated in a similar manner as the toolpath for crafting the object. The toolpath can be optimized in relation to speed, area covered, and the number of passes over a specific area to provide optimal carrier removal.

The carrier removal can be performed on a layer by layer basis. Alternatively, the carrier removal can also be optimized, so that several layers of the crafting material is deposited before the carrier removal is performed.

The carrier removal mechanism can be in the form of an infrared radiating component, that can heat a specific area of the crafting medium to evaporate the carrier or solvent, or stated differently the heat applied would serve to, in part dry the layers. The carrier removal mechanism can be in the form of a hot gas blowing mechanism to evaporate and remove the carrier or solvent. The gas can be air or another appropriate gas or mixture of gases. The carrier removal mechanism can be in the form of a heated component that heats a specific area of the crafting medium by contact and subsequently evaporates the carrier to provide drying of the area of the crafting medium layer. For an aqueous solvent or solvent system, the drying mechanism can be in the form of a local microwave radiating component that heats up a specific area of the crafting medium by microwave heating and evaporates the carrier.

To allow for an increased rate of the drying of each layer, a separate process can utilize a full width moving head 501. The moving head 501 can include a means 301 for transporting the carrier away from the print area that can include a suction or aspiration mechanism 302. The moving head 501 can scan the crafting medium layer after completion of one or more layers. See FIG. 5 for a schematic example of a full width moving head. See FIG. 6 for an illustration of the movement of the full width moving head 501 across a layer The solid arrows illustrate the path of such movement.

An additional means for improving the carrier removal function for all the mentioned carrier removal processes is to lower the pressure of the atmosphere surrounding the crafting medium, thereby facilitating carrier removal or evaporation with a lower temperature requirement on the removal function, or to enable the carrier to evaporate by itself. This method can further be augmented by the use of a vacuum.

Another way to remove the carrier from the crafting medium is to employ a heating means 701 to heat the crafting medium at the extrusion orifice. The temperature to which the crafting medium is heated will depend upon the composition of the crafting medium. For example, for a crafting medium comprising an aqueous solvent, a useful temperature range can be from about 40-100° C. Other temperature ranges would be appropriate for non-aqueous solvent systems depending on the boiling point of the solvent system. This heating will enable the carrier to evaporate instantly or rapidly from the crafting material as deposited 702. In addition, a means 301 for transporting the carrier away from the print area can be employed which can include a suction or aspiration mechanism 302. See FIG. 7 for a schematic example.

An important factor in crafting a body for post processing such as sintering is to achieve a fully dense body or part of the body. By fully dense is meant that the crafting medium should be deposited in a manner so that there are no voids between the layers and the one or more lines comprising the layers. A fully dense body or part of body is needed to achieve, for example, optimal thermal and mechanical properties. When depositing a crafting medium in a layer by layer basis from a line by line printing manner there is a risk of undesired voids 801 between the layer and lines. See FIG. 8 for an illustration of this scenario.

A solution for avoiding this risk can be to overfill the mold with the crafting medium and then to scrape away the excess. However, it will then be necessary to remove the excess crafting material. The excess material could be scraped off while the crafting medium is still we, prior to the use of a drying and/or heating apparatus or in a state where the drying and/or heating apparatus has only partially removed the carrier. This scraping can involve the use of a single pass scraper. Alternatively, a device that is associated with or partially or completely surrounds the nozzle to scrape off and removes the excess crafting medium as it is deposited can be employed.

One embodiment, as illustrated in FIGS. 9 and 10, is to use a deposition nozzle having an orifice 114 for extruding the crafting medium 117, where the nozzle includes a geometry for scraping off the excess material 902 just after the extrusion point. The scraping function is further realized by a by a partial or completely circular knife/wedge like geometry 901, and optionally with a suction mechanism for transporting the excess material away from the print area (not shown). During the deposition of the crafting medium, the deposition rate is for example 0.5%-10% higher than the theoretical for filling the specific voids, and the excess material 902 will create ridges on top of the surface of the layer 117. The circular knife/wedge 901 will then cut/remove the excess material 902 to achieve a flat, fully dense surface.

Another embodiment uses a means for removing the excess deposited material that is separate from the means used to deposit it, including a scraping knife/wedge. This separate component can optionally have a suction mechanism for transporting the excess material away from the print area.

Another embodiment, FIG. 11, uses a full width scraping component 1101 in the form of a knife/wedge, where the component will scan the complete layer after deposition to remove the excess material 902. The scanning of the component can be performed in a single pass such that one traversing motion is required to affect the entire layer. Optionally a suction mechanism 1102 can be used to remove the excess material from the print area. After the removal of the excess material from the print area, the layer is processed to remove the carrier, i.e. to dry the layer, before the next layer is deposited.

In another embodiment, the layer of the crafting medium is dried prior to removal of the excess material. See FIG, 12 for an illustration of a process for removing the dried excess material 1203 with a milling means 1201 with an option suction mechanism 1202 for transporting the excess material away from the print area. FIG. 13 illustrates the process of removing the excess material with a separate moving head 1302 with a milling means to remove the excess material along a toolpath 1301. The toolpath can be generated in a similar manner as the toolpath for crafting the object. The toolpath can be optimized in relation to speed, the area covered, and the number of passes over a specific area to allow optimal removal of the excess dried crafting medium.

The excess material removal mechanism can be a rotating knife or milling type mechanism. In addition, a suction mechanism can be used to remove the excess material from the print area. To allow for an increased rate of removal of the excess material from each layer, a separate process can be employed using a full width moving component including a means for removing the excess material. This component will scan the crafting medium layer after completion of 1 or more layers while enabling the excess material removal function. The excess material removal mechanism can be a rotating knife or milling type mechanism. In addition, a suction mechanism can be used to remove the excess material from the print area. The excess material removal can also be optimized, so that several layers of the crafting material is deposited before the excess material removal is performed.

Crafting Medium

Although a wide variety of crafting media can be used with the methods and systems of the present invention, a particularly useful crafting medium contains a very low concentration of the binder organic base materials, such as starches, cellulose, cellulose derivatives, agar, etc., and around 15 to 60 volume % water. The binding organic base material content can be varied from 1 to 10 volume %. The binder can act as glue between the powder particles, and also as filler between the particles. The method of preparation of the three-dimensional object also includes the step of drying on a layer-by-layer basis. The drying is a continuous process in the present invention and can remove most of the water and/or other solvents or carriers from the binder composite material from each layer after depositing. The crafting media useful herein are generally in the form of a paste.

An exemplary crafting material useful herein comprises:

-   (i) from about 40% to about 80% by volume basis of a powder selected     from metal powders, ceramic powders, and combinations, thereof; -   (ii) from about 0.5% to about 10% by volume of a binder; and -   (iii) from about 15% to about 60% by volume of an aqueous solvent.

An exemplary crafting material useful herein comprises:

-   (i) from about 40% to about 80% by volume basis of a powder selected     from metal powders, ceramic powders, and combinations, thereof; -   (ii) from about 0.5% to about 10% by volume of a binder; and -   (iii) from about 15% to about 60% by volume of a non-aqueous     solvent.

Another crafting material useful herein comprises,

-   (i) from about 60% to about 70% by volume basis of a powder; -   (ii) from about 1% to about 5% by volume of a binder; and -   (iii) from about 25% to about 35% by volume of an aqueous solvent.

Another crafting material useful herein comprises,

-   (i) from about 60% to about 70% by volume basis of a powder; -   (ii) from about 1% to about 5% by volume of a binder; and -   (iii) from about 25% to about 35% by volume of a non-aqueous     solvent.

The solvent or carrier for the crafting material can be an aqueous solvent. Such an aqueous solvent can be solely or primarily water, or can comprise other solvent materials which are generally water miscible. In other embodiments, a nonaqueous solvent or mixtures of non-aqueous solvents can be employed. Such non-aqueous solvents can be selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, C4-alcohols, 2-ethoxyethanol, 2-ethyl hexanol, 1,2-dichloroethane, diisopropyl amine, isoamyl alcohol, propyl acetate, isopropyl acetate, and mixtures thereof. Also, contemplated are azeotropes.

Several materials can be used as the leaving component, i.e. the solvent or carrier, in the deposition technique involving continuous, layer-by-layer drying. One example of a departing component is water, with a vapor pressure of about 2.4 kPa. Higher vapor pressures, i.e. low boiling points, are in general preferred, as they will require less energy to drive away from the deposited part. However, including materials with vapor pressures which are very high as compared to water (acetaldehyde, for example) can in some instances cause difficulties with layer-to-layer and strand-to-strand bonding if the leaving component departs prior to the formation of a significant bond. In this case controlled drying, achieved via depression of the print temperature, can be employed during formation of the object. After formation of the object, the temperature (or other thermodynamic variable) can be changed to complete the removal of the leaving component.

Solvents used can be aqueous (e.g., water, and water with salts or surfactants), organic and primarily carbon based solvents, and organic solvents with halogen groups, fluorinated organic solvents, or mixtures of any of those aforementioned items. Mixtures of components may be chosen such that when the components leave the part, the components leave in a proportion identical or substantially similar to the proportion of the components in the deposited material.

In addition to the list provided below, materials such as dichloroethane, diiodoethane, fluorinated or chlorinated refrigerants, or degreaser materials as manufactured by DuPont (Operteron) or MicroCare (Tergo) can be used. Further, solvent drying specialty fluids added to liquids such as water or ethanol (and their mixtures), can be used. Such a solvent drying specialty fluid is Vertrel XP10 Solvent Drying Specialty fluid by MicroCare.

In the three-dimensional printing process, it is necessary to use binders to provide rigidity to the crafting medium of the object during fabrication. Different types of binding materials can be used in these three-dimensional printing processes. Organic binders, such as epoxy, polyurethane, agar-agar, starch, cellulosic materials, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dammar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide , polycarboxylic acids (polyacrylic acid), polycarboxylate ethers, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, Carboxymethyl cellulose, etc. can be used while Inorganic binders, such as magnesium oxides, magnesic, cement, sorel cement, salts, etc. are used.

The three-dimensional objects with a powder plus binder constitution for sintering can pose several problems. The binder can be difficult to remove because it needs to be dissolved or burned out after the object is finished. The binder can also be hazardous and or can require toxic substances to dissolve it away. While removing the binder there is a risk for developing cracks and deformities in the resulting object. Furthermore, methods of three-dimensional printing using clay or ceramic materials and preparing a mold are also well known in the prior art documents. Most of these prior art documents discusses the drying or heating of the mold or clay paste post processing. A major problem is cracking of the deposited object when the drying is carried out at the end of the full deposition processing. Cracks and unevenness can develop on the mold or on the object. The present invention is providing solution to solve these problems of cracks and unevenness of the object or the mold.

A solution to this cracking problem is taught in the present patent application. This solution is achieved by providing a crafting medium comprising a metal or ceramic, binder organic base materials, and water. The crafting medium which is in the paste form includes 40 volume %-80 volume % metal/ceramic powder, 1 volume %-10 volume % organic base material, and 15 volume %-60 volume % water. The metal or ceramic powder particle size is in the range from 0.1-100 micrometers.

In another embodiment of the invention, the crafting medium comprises microscopic particles of a metal, such as silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel or alloys or combinations thereof, and also oxides of these metals, mixed with the binder, organic base material, and water. Also, additional corrosion inhibitors or sintering aiding or lubrication additives, generally in the range of 0.1-2 volume %, can be added.

In another embodiment, the powder is instead a ceramic powder such as silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate and zirconia mixed with the binder organic base material and water. Also additional corrosion inhibitors, sintering aiding or lubrication additives, generally in the range of 0.1-2 volume %, can be added.

In both these immediately foregoing embodiments, the binder organic base material can be polyurethane, agar-agar, starch, cellulosic materials, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dammar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide , polycarboxylic acids (polyacrylic acid), polycarboxylate ethers, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, Carboxymethyl cellulose, or combinations thereof.

Sintering aids such as salts, gum rosin or pine rosin, isopropyl alcohol, propylene glycol, copper oxides, other metal oxides, low melting point metals or alkaline earth metals can be used. Lubricants aids such as essential oils, glycerin, zinc stearate or other stearates, carbon black, silica and ferrous oxide can be used. Corrosion inhibitors such as those selected from the group consisting of nitrates of lithium, sodium, potassium, calcium, magnesium, zinc, cobalt, iron, chromium, and copper, and the nitrite of lithium, sodium, potassium, calcium, magnesium, zinc, can be used.

With the compositions and processes of the present invention, substantially all of the moisture, i.e. the water, and other solvent or carrier components for the binder of the crafting medium is removed immediately after deposition of each layer by use of the drying means or apparatus. By “substantially all of the moisture” is meant that at least about 90% by weight, and in further embodiments at least about 95% by weight, and yet in further embodiments at least about 99% by weight of the water and other solvent or carrier components are removed. This novel method of three-dimensional object building does not require the use of a post-processing debinding step. Furthermore, the present invention also provides a system for improved drying in a controlled manner of a paste based crafting medium during three-dimensional printing and methods thereof. The drying means or apparatus can take the forms described above. These means make drying possible after printing each layer of the object (both mold and paste).

EXAMPLES

The following examples further described and demonstrate embodiments within the scope of the present invention. The Examples are given solely for purpose of illustration and are not to be construed as limitations of the present invention, as many variations thereof are possible without departing from the spirit and scope of the invention.

Example 1 Crafting Medium and Process for Making

A crafting medium comprising the following components was prepared. The components are each on a volume % basis.

Stainless steel powder 17-4: 62%

Distilled water: 32%

Arrow root powder: 4%

Xanthan gum 1%

Polycarboxylate ether 1%

A premix of the water and arrow root is prepared by heated to 80° C. with stirring. The premix is then cooled to room temperature. A separate premix of xanthan gum and the polycarboxylate ether is made by combining them with stirring to form a thick paste. Next, the stainless steel powder and the xanthan gum premix are added to the arrow root premix and combined using a mechanical stirrer.

The resulting paste is useful for three-dimensional printing. The paste can be printed on a line-by-line and layer-by-layer basis in conjunction with a mold layer. Each deposited paste layer is dried according to the present invention. The resulting three-dimensional object is then subsequently debound and then sintered to provide the stainless steel three-dimensional object.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-discussed embodiments may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description.

The benefits and advantages which may be provided by the present invention have been described above with regard to specific embodiments. These benefits and advantages, and any elements or limitations that may cause them to occur or to become more pronounced are not to be construed as critical, required, or essential features of any or all of the embodiments.

While the present invention has been described with reference to particular embodiments, it should be understood that the embodiments are illustrative and that the scope of the invention is not limited to these embodiments. Many variations, modifications, additions and improvements to the embodiments described above are possible. It is contemplated that these variations, modifications, additions and improvements fall within the scope of the invention.

Incorporation by Reference

The entire disclosure of each of the patent documents, including certificates of correction, patent application documents, scientific articles, governmental reports, websites, and other references referred to herein is incorporated by reference herein in its entirety for all purposes. In case of a conflict in terminology, the present specification controls.

Equivalents

The invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are to be considered in all respects illustrative rather than limiting on the invention described herein. In the various embodiments of the methods and systems of the present invention, where the term comprises is used with respect to the recited steps of the methods or components of the compositions, it is also contemplated that the methods and compositions consist essentially of, or consist of, the recited steps or components. Furthermore, it should be understood that the order of steps or order for performing certain actions is immaterial so long as the invention remains operable. Moreover, two or more steps or actions can be conducted simultaneously.

In the specification, the singular forms also include the plural forms, unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the case of conflict, the present specification will control.

Furthermore, it should be recognized that in certain instances a composition can be described as being composed of the components prior to mixing, or prior to a further processing step such as drying, binder removal, heating, sintering, etc. It is recognized that certain components can further react or be transformed into new materials.

All percentages and ratios used herein are on a volume (volume/volume) or weight (weight/weight) basis as shown, or otherwise indicated. 

What is claimed is:
 1. A method for three-dimensionally printing a metal or ceramic object from a paste-based crafting medium comprising the steps of: (a) depositing a layer of a crafting medium with a print head, and (b) drying the deposited layer from step (a) with a drying means, wherein steps (a) and (b) are performed prior to deposition of a further crafting medium layer.
 2. A method according to claim 1 wherein the drying step (b) is selected from, (A) point drying of the deposited layer, or (B) full area drying of the deposited layer.
 3. A method according to claim 1 wherein the drying means is provided by a drying head selected from a radiating heater, an infra-red heater, a circulating convective heater, a hot gas blowing heater, a contact heater, a resistance heater, or a microwave heater.
 4. A method according to claim 3 wherein the drying head follows (A) the same trajectory as the print head or (B) follows a trajectory that is different from that of the print head.
 5. A method according to claim 1 wherein the deposited layer of the crafting medium is heated to a temperature from about 20° C. to about 100° C. for deposition.
 6. A method according to claim 1 comprising drying the deposited layer from step (a) while simultaneously or subsequently decreasing the atmospheric pressure surrounding the crafting medium to facilitate said drying.
 7. A method according to claim 1 wherein the crafting medium comprises: (i) from about 40% to about 80% by volume basis of a powder selected from metal powders, ceramic powders, and combinations, thereof; (ii) from about 0.5% to about 10% by volume of a binder; and (iii) from about 15% to about 60% by volume of an aqueous solvent.
 8. A method according to claim 1 wherein the crafting medium comprises: (i) from about 40% to about 80% by volume basis of a powder selected from metal powders, ceramic powders, and combinations, thereof; (ii) from about 0.5% to about 10% by volume of a binder; and (iii) from about 15% to about 60% by volume of a non-aqueous solvent.
 9. A method according to claim 7 wherein the drying step (b) removes substantially all of the aqueous solvent from the deposited layer (a).
 10. A method according to claim 7 wherein the drying step (b) removes substantially all of the non-aqueous solvent from the deposited layer (a).
 11. A method according to claim 7 wherein the metal powder is selected from silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel, metal alloys, and combinations thereof, or wherein the ceramic powder is selected from silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate, zirconia, and combinations thereof.
 12. A method according to claim 7 wherein the binder is selected from organic binders, inorganic binders, and combinations thereof.
 13. A method according to claim 7 wherein said aqueous solvent is selected from water, or water in combination with one or more non-aqueous solvents selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, and mixtures thereof.
 14. A method according to claim 8 wherein said non-aqueous solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, and mixtures thereof.
 15. A method for three-dimensionally printing a metal or ceramic object from a paste-based crafting medium comprising the steps of: (a) depositing a mold layer from a print head, (b) depositing a layer of a crafting medium with a print head within the confines of the mold layer, (c) drying the deposited layer from step (b) with a drying means, wherein steps (a), (b), and (c) are performed prior to deposition of a further crafting medium layer.
 16. A method according to claim 15 wherein the crafting medium deposited in step (b) is deposited at a volume in excess of the volume defined by the mold layer, and wherein the excess crafting medium deposited in step (b) is (A) removed prior to drying in step (c) or is (B) removed subsequent to drying in step (c).
 17. A method according to claim 15 wherein the mold layer comprises a thermoplastic polymer.
 18. A three-dimensionally printed article of manufacture prepared according to the method of claim
 1. 19. A three-dimensionally printed article according to claim 18 prior to sintering.
 20. A system for continuously drying a paste-based crafting medium during three-dimensional printing of a metal or ceramic object comprising: (a) a print head for depositing a layer of a crafting medium, and (b) a drying means for subsequently drying each deposited layer (a), wherein steps (a) and (b) are performed prior to deposition of a further crafting medium layer. 